The present invention is directed generally to battery chargers, and more specifically to a battery charger having automatic trickle charge, fast charge and discharge modes.
Portable electronic devices such as two-way radios, receivers, recorders and test equipment, which may see frequent use over an extended period of time, typically utilize rechargeable batteries which can be recharged after use, thereby avoiding the expense and inconvenience of installing new batteries.
Typically, the batteries of the devices are contained within a removable battery pack. During operation the battery pack is installed in the device. When the batteries become depleted, the battery pack is removed and inserted into a charger, which contains all necessary power supply and control circuitry for bringing the batteries of the battery pack up to full charge. Preferably, the recharging procedure takes place initially at a fast charge rate, and then at a trickle charge rate, and is entirely automatic, requiring no attention or control input by the operator.
One type of rechargeable battery which has proven particularly attractive for this purpose is the nickel cadmium-type battery. This battery combines high current capacity with long shelf life, and is relatively economical to manufacture. Unfortunately, such nickel cadmium batteries are subject to "memory effect", wherein they quickly become depleted in use, notwithstanding having been recently brought up to full charge. It has been determined that this effect is caused by repetitive shallow discharges and sustained overcharge periods, and can be avoided by subjecting the batteries to a deep discharge prior to charging.
The present invention is directed to a battery charger which accomplishes the necessary pre-charge deep discharge, as well as the subsequent conventional fast charge and trickle charge, completely automatically and without input from the operator.
Accordingly, it is a general object of the present invention to provide a new and improved battery charger.
It is a further object of the present invention to provide a battery charger which is fully automatic and requires no monitoring or input from the operator.
It is a further object of the present invention to provide a battery charger which includes discharge, fast charge and trickle charge modes automatically as required by the condition of the battery.
It is a further object of the present invention to provide a battery charger which provides an operator-initiated deep discharge mode which automatically reverts to fast charge and trickle charge modes in accordance with the terminal voltage of the battery.